Yes, will be clear in first line of the notebook (with setprecision used to go above the std 128bit BigInt). I believe this is part of the 'base' Julia distro now.
With Julia, you just use "big" and go from there. See syntax in the notebook example. Once a variable has the Bigtype associated to it, it transfers along the chain of calculations (so don't need to explicitly use every step, it just works).
Total setup time and getting into the notebook in the pastebin should be under an hour.
When you have running, I can drop another notebook that calculates a set of primes to use for the prime_small * c step.
Nice thing is sharing notebook code is tiny, and then you can generate the big stuff locally yourself.
Regarding packages, after adding, when calling in code you enter "using PackageName" and that's it.